The present invention relates to a solder bath of wave soldering systems, and more specifically, to an apparatus applied to the wave former for increasing the wave height of molten solder.
With the continuing advances and developments of electrical manufactures, the electrical products in new generation have more developed and complicated capability to provide peoples more convenient and comfortable life. For instance, in computer industry, because the manufacture and packaging techniques of integrated circuits are promoted and matured, the high quality multimedia personal computers are widely used. The expenditure enhancement for computers and peripheral products cause the popularization and more vigorous development thereof. However, when the performances of chips are promoted, the amounts of leads to package components on the printed circuit boards (PCBs) also are continuously enhanced. Thus the layout of printed circuit boards becomes more fine and complex. And the difficulties to mount and solder components thereon are also enhanced.
In general, the key factor of the yields of mounting assembly parts onto printed circuit boards is the leads soldering procedure of components. Especially when the amounts of leads for packaging are increased and the arrangement thereof become highly concentrated, the effective reductions of defects such as bridge, dewetting, blow hole, and etc. can promote the yields of PCBs productions and reduce the failure opportunities of components. In prior art the wave soldering procedures are mainly applied to assembly printed circuit boards for furthering mass productions. And in wave soldering process, the molten solder is driven by a motor pump and forced upward into the through holes beneath the printed circuit boards which are transported obliquely to pass the soldering wave.
Please refer to FIG. 1, the current wave soldering system 10 is illustrated. In the wave soldering system 10, a solder bath 12 is applied to contain molten solder, and a motor pump 14 mounted beside the solder bath 12 can rotate its fan blades to drive the molten solder. The molten solder gushed upwards from a wave former 16 disposed in the solder bath 12 forms the rising solder wave. And printed circuit boards 20 can be transferred above the solder bath 12 through inclined transport rails 18. Thus the rising solder wave can fill into the through holes beneath the printed circuit boards to solder the leads of components. It is noted that in the wave soldering procedure the printed circuit board 20 is disposed onto a carrier formed of aluminum alloy or fiberglass wherein the carrier has some hollows for exposing the soldering areas of the printed circuit board. Then the finger 22 chained beneath the transport rails 18 can grab two side of the carrier to transfer the printed circuit board 20 via the transport rails 18.
In general, the printed circuit board 20 is coated flux and preheated first in the front part 24 of the transport rails 18. The flux is applied to clean the surfaces of the soldering metal and to avoid rustiness in atmosphere at high temperature. Besides, the flux is also applied to spread thermal energy uniformly for enhancing the performance of the soldering points. The typical flux coating procedures include foaming type, spraying type, and soaking type. As to the subsequent preheat procedure is applied to dispel the volatility parts of the flux for promoting the temperatures of the printed circuit boards to enhance the flux activity and to prove the capability of filling molten solder into through holes. The typical preheating procedure is to apply infrared tubes beneath the carriers to illuminate the printed circuit boards for getting the predetermined temperature.
Please refer to FIG. 2, the lateral view of the solder bath 12 in wave soldering procedure is shown. The molten solder gushed upwards from the wave former 16 reflows downward along the sidewalls of the solder bath 12, and then is retrieved in the recycled trough around the solder bath 12. As to the carrier 26 containing the printed circuit board 20 can pass the solder wave of molten solder 24 via the inclined transport rails. Thus the molten solder can fill the through holes beneath the printed circuit board 20 to form solder points.
It is noted that in the typical wave soldering system the height of solder wave can not exceed 12 mm, so when this type of system is applied to soldering the printed circuit board with components mounted on both sides thereof, the rising molten solder is incapable of full filling the through holes of the printed circuit boards. Especially this type of printed circuit board 20 with components both sides usually has a large thickness, so the through holes formed therein also have large depths. And relatively, the carrier 26 applied to contain this type of printed circuit board 20 also has a large depth to effective protect the components thereon.
Therefore the yields of wave soldering procedures will be reduced amplitudely. Especially when the component 21 mounted on the first side of the printed circuit board 20 has a large height, the total height of the component 21 and carrier 26 is too large to effective fill the through hole from the second side of the printed circuit board 20. Thus the defects such as voids and broken circuits usually occur at the soldering points.
In prior art the rotation rate of the motor is increased to have higher soldering wave for the thick printed circuit board in wave soldering procedure. However in practical manufacturing process, the motor pump operated at high rotation rate is unstable and usually make turbulence in the molten solder. Thus the yield of wave soldering is becoming unstable. For solving this issue, the soldering furnace 30 as shown in FIG. 3 is introduced to soldering the thick printed circuit boards. The overflow of molten solder in solder bath 34 of the soldering furnace 30 can be controlled via adjusting the buttons on the control planet 32. The operators then put the printed circuit boards by hands on the solder bath 34 to perform the soldering procedure.
However due to the solder bath 34 is exposed out of soldering furnace 30, the air pollution is serious in soldering procedures and easy injure the operators. Beside when the numerous component leads are highly concentrated arranged, short circuits usually occur and reduce the quality of soldering points. Further, it is necessary to transfer the printed circuit board with large height out of the wave soldering production line first; and then to have the soldering procedures with soldering furnaces. Therefore the throughput is decreased and much cost and man effects are required to measure the printed circuit boards. So how to increase height of soldering wave and to keep the stability of soldering wave is a momentous issue for the integrated circuit packaging industry.
A purpose of the present invention is to provide a block board mounted onto the enclosing walls of the wave former to increase the height of enclosing walls and to make higher solder wave.
Another purpose of the present invention in to provide a gland mounted on the wave former to press the molten solder for increasing wave height of the molten solder.
Further a purpose of the present invention in to provide an apparatus applied to the wave soldering system for providing higher and stable molten solder wave.
The present invention discloses an apparatus applied to the wave soldering system for increasing wave height of molten solder. The wave soldering system comprises the following elements. A solder bath is applied to contain molten solder. A motor pump is disposed besides the solder bath having fan blades extended into the solder bath for driving the molten solders upwardly. A wave former is disposed in the solder bath to gush the molten solder upwardly to form solder wave. A block board is mounted along top edges of enclosing walls of the wave former for increasing the heights of the enclosing walls. And a gland is pressed downward along inner surfaces of the enclosing walls of the wave former to press partial molten solder and to form higher wave via the opening of the wave former uncovered by the gland.